The L grade is a high grade Baker hammerless. If I remember correctly Baker introduced the L grade around 1905 and it eventually became the Expert grade in later years putting it just one level below their top of the line Deluxe grade. A lot of the Baker guns are not marked with a grade designation and I don't remember off the top of my head whether the L grade guns were typically marked but I don't think they were.
Take a look here:
http://www.bakercollectors.com/index.php?p=1_10_PhotosScroll about 2/3 of the way down the page and there are a few images of a couple nice L grade Bakers.
There are a couple members here that will be able give better advice than I can on what a fair offer might be. It's rare to see an L grade or higher Baker for sale, so there's just not much to go by.
Grant - If you decide you are not interested in purchasing it please let me know. PM sent